Sound-translating chamber



Oct. 8, 1929.

P. ROBBINS SOUND TRANSLATING CHAMBER Filed Sept. 14, '1927 INVENTDH.

Patented Oct. 8, 1929 PERCY A. ROBBINS, OI HIGHLAND PARK, ILLINOISsoimn-rmsnarmo cnumna Application fled September 14, 1927. Serial No.219,548.

This invention relates to chambers in which sounds are recorded ortranslated for mechanical or electrical reproduction and which arecommonly known as studios.

The usual practice in studios is to generate sounds by setting the airparticles in motion. These motions are propagated through theatmosphere, being directed to diaphragm which translate the sound wavesmto mechanical motion of the diaphragms for recording or for furthertranslation and transmission.

This entire method of propagating and translating sounds is ineflicientbecause air is an attenuated medium of light mass and can only transmitthe required sound energy by virtue of high velocities imparted to t eair particles, that is, each vibration must be of great amplitude" inorder that the air part1- cles may attain the necessary velocity totransmit the impressed sound energy.

Sound producing instruments vibrate at comparatively low amplitudes, andin most cases attempts to increase the amplitudes of v1- brations resultin the production of overtones, because the inertia of the vibratingreeds, or strings or vocal chords, as the case may be, tends to damp theincreased amplitudes and break up the vibratin structure into an insocreased number of no es and anodes.

Thus although the performers of instruinental or vocal music or soundspossess a surplus of power, they cannot use that surplus power beyond acertain limit because of the difficulty in avoiding the productlon ofundesirable overtones and harshnoises.

In a like manner the conversion of the air vibrations into vibrations ofa diaphragm is ineflicient because the mass of the diaphragm isnecessarily great, for it must be made of available materials ofconstruction and must possess certain structural strength regardless ofits function to vibrate freely.

Obviously then, in order to increase the sound energy which may besatisfactorily emitted by sound producing instruments and translate thesound into mechanical movements of a diaphragm, the medium throu h whichthe sound is pro agated from t e source to the diaphragm s ould be amedium of comparatively great mass, and a dense gaseous medium is bestadapted for the purpose.

My object, therefore, is to devise means for utilizing this principle inthe manufacture of phonograph records, or in radio broadcasting.

- I attain my object by employing as a studio a chamber provided with anair lock for the entrance and exit of performers. Within this chamber anair pressure is maintained which is greater than normal atmosphericpressure. i

As the performers in the denser atmosphere of the studio are forced tobreathe in an excess of oxygen per cubic foot of air inspired,

- it will be advisable to modify the atmosphere by the introduction of asuitable proportion of an inert gas such as helium or an excess ofnitrogen, thus avoiding the danger of excessive oxydization of the bloodand lung tissues.

To avoid confusion of sounds due to reverberations and reflectionswithin the studio it is essential that the walls and ceiling of thestudio be non-reflecting. This can be accomplished most effectively byhanging the walls with strings or ropes or other like strips of softflexible material, preferably arranged in a series of rows spaced fromone another and the walls of the chamber, and by suspending verticallyfromthe eeilin a great number of strings or ropes, preferably of unequallengths spaced at random.

While I contemplate the use of the common types of broadcastingmicrophones and phonographic recording devices located in the usualmanner within the studio, there are certain advantages to be gained bynot having this apparatus so located.

I therefore incorporate the translatin diaphragm as a part of the studiowall, an by this means remove from the studio all but the exposed faceof the diaphragm, Noises emanating from the recording or translatingdevices are thus eliminated from the studio, and the presence in thestudio of operatives whose duty it is to regulate the recording andtranslating devices is not necessary.

In some cases it is desirable that photo- 100 graphs shall be taken ofthe performers while in the studio, and as the space within the studiowill be more or less restricted, and the satisfactory photographicresults,'produces a great deal of heat, and as it is most desirable thatthis heat be excluded from the studio I arrange suitable windows forprojecting light into the studio from outside sources.

' The space within the studio being restricted it is necessary toprovide a means for changing the air and I accomplish this by means ofan exhaust valve which is connected to the studio through a mufiledpassage.

The invention is hereinafter more fully described and is illustrated inthe accompanying drawings in which Fig. 1 is a diagrammatical sectionalview of apparatus constructed in accordance with my invention;

Fig. 2 a sectional detail showing the method of securing an adjustablewindow in position; Fig. 3 a vertical sectional detail of part of thewall and ceiling of the chamber illustrating the method of draping toprevent sound reflection.

In the drawings like numerals of reference indicate corresponding partsin the different figures.

1 is the sound translating chamber, which will usually be formed ofmetal, or otherwise constructed so as to contain air at superatmospheric pressure. This chamber is provided for the purpose ofentrance and exit with an air lock 2 of known type. As such devices arewell known in the art, a specific description of its details is omitted.

Means are provided for introducing air under pressure into the chamber1, and for rendering this pressure constant. purpose provide thegasometer 3 which may be 0 any known type. From this gasometer a pipe 4leads to the interior of the chamber 1. This pipe is provided with acontrolling valve 5, preferably within the chamber 1. A valve controlledoutlet 6 is also provided, whereby air within the chamber may be allowedto escape under the control of any one within the chamber.

With the interior of the gasometer communicates a pipe 7 preferablyprovided with a check valve 8 to prevent back flow. A sec- 'ond pipe 9is provided also communicating with the interior of the gasometer,preferably through part of the ipe 7. Thls pipe is also provided with achec valve 10. Through one of these pipes air under pressure may beintroduced into the interior of the gasometer,

For this while through the other any gas which it may be desirableto useto modify the atmosphere of the chamber may be introduced.

The sound translating diaphragm 11 is set in an opening 12 formed in thewall of the chamber so thatv there is no need for the presence in thestudio of any operatives whose duty it is to regulate the recording andtranslating devices. Certain possibilities of the introduction ofdisturbing noises are thus eliminated.

As it is sometimes desired to take photographs of performers within thechamber and, as it is very desirable that noise producing instruments bekept outside the studio, I provide one or more windows in the studio,such as illustrated in Fig. 2. In an opening in the wall of the chamber1 is fitted a frame 13, in which frame is formed an opening 14 having asegmento-spherical wall. In the opening 14' is fitted a frame 15 havingan opening therein fitted with the glass frame 16. The frame 15 willhave an air tight fit with the frame 18, and may be set up to inclinethe pane 16 in any desired position. The frame 13 must necessarily bemade in halves, secured together by the bolts 17 in order that the frame15 may be positioned therein.

Trouble, due to sound reflection, is likely to be increased by the denseatmosphere, hence I employ the special means for breaking up reflectionsillustrated in Fig. 3. Brackets 18 are secured about the wall of thechamber. From these brackets are hung a series of rows of strings orropes 19 or other like strips of soft flexible material. From theceiling are hung a series of strings or ropes of soft flexible material,preferably of different lengths, so as to present any irregular undersurface, if such it may be called.

From the above description the method of use of the sound translatingchamber will be reasonably clear. A. suflicient amount of atmosphericair is introduced into the chamber at approximately the desiredpressure, which will usually be less than thirty-five pounds per squareinch. This air will be modified by the introduction through one of thepipes connected to the gasometer of a suitable pro portion of an inertgas such as nitrogen or helium. As may be necessary, air is allowed toescape through the pipe 6, the gasometer maintaining the pressure untila further supply of air and inert gas is supplied through the gasometer.The performers enter or leave from time to time through the air lock theoperation of which, of course, assists in the changing of the air withinthe chamber.

From the above description it will be seen that I have devised a soundtranslating chamber, which will satisfactorily attain the objects of myinvention as set out in the preamble to the specification.

What I claim is:

1. A studio in which sounds may be produced for record or translation,comprising a closed chamber containing air under a pressure eater thanthat of the air outside the cham er, and provided with a vibratablediaphra exposed at one side to the pressure within t e chamber and atthe other to the atmosphere outside the chamber.

2. A studio in which sounds may be produced for record or translation,comprising a closed chamber containing air under a pressure reater thanthat of the air outside the cham er and provided with a windowadjustable to positions normal to the light rays passing throu h it,whereby reflection and refraction 0 such rays may be avoided.

31. A studio in which sounds may be pro- 'duced for record ortranslation, comprising a closed chamber containing air under a pressureeater than that of the air outside the cham r and having its wallsdraped with stri s of soft flexible material suspended vertica y bytheir upper ends.

4. A studio in which sounds may be produced for record or translation,comprising a closed chamber containing air under a pressure eater thanthat of the air outside the charm r and having its ceiling draped withstrips of soft flexible material suspended verticall by their upgerends.

Signe at Highlan day of September, 1927.

PERCY A. ROBBINS.

Park, 111., this 20th

